Microelectronics chips such as integrated circuits are made from comparatively large wafers of semiconductor material by processes known as wafer fabrication. A fundamental step in wafer fabrication is photolithographic masking and etching which is used to define selected regions of the wafer for such processing as etching or impurity diffusion. The photolithography process requires a photoresist coating which is first selectively developed to permit selective processing, and which is thereafter removed by a chemical known as a photoresist stripper. After photoresist stripping, the photoresist stripper must in turn be removed from the wafer by a process known as rinsing.
As described, for example, in the paper, "A Simple Model for Rinsing," A. Tonti, Electrochemical Society Meeting, October 1991, one method of rinsing is to immerse the wafers in a tank into which water and nitrogen are pumped so that the water overflows the tank. Another method, known as the quick dump rinse (QDR) method, requires water in which wafers are contained to be quickly emptied or dumped.
A problem with the various rinsing methods using water is the tendency of aluminum layers on the surface of the wafer, such as are used as conductors and bonding pads, to corrode during the rinse cycle. Such corrosion is typically characterized by pits in the surface of the aluminum conductors which, with the progressive reduction in the size of conductors on the surface of microchips, become a progressively more serious problem. Our experiments show that rinsing in isopropyl alcohol can reduce pitting, but such use is undesirable because isopropyl alcohol is more expensive than water, and it constitutes a waste that may be harmful to the environment. Thus, there is a continued long-felt need in the industry for a method for rinsing photoresist stripper from wafer surfaces which does not corrode aluminum conductors on the wafers and which is not unduly expensive or harmful to the environment.